Helo,
I have installed aapanel on Alamalinux 9 OS several times and I always have the same problem with phpmyadmin.
Everything was installed as LAMP should be and URL phpmyadmin works normally. After the first server restart, when I try to access the phpmyadmin URL, I get error 503. Aapanel has LAMP installed, I tried to install OS Almalinux 8 later and that problem does not exist related to phpmyadmin.
On Almalinux 8 everything works normally when the server is restarted, the phpmyadmin URL can be accessed and there is no 503 error. Does anyone have the same problem as me with aapanel (LAMP) and OS Almalinux 9 ?